Insofar as applicant is aware, the most pertinent art to the present invention is contained in U.S. Pat. No. 4,049, 841 issued to Coker et al, Sept. 20, 1977 and U.S. Pat. No. 4,243,497 issued to Nicolas et al on Jan. 6, 1981. Also pertinent are the disclosures set forth in published European Patent Application No. 009,406 published Apr. 2, 1980 naming D. E. Brown et al, inventors and the Hall et al U.S. Pat. No. 4,200,515 of Apr. 29, 1980.
Coker et al described cathodes for the production of hydrogen in aqueous chlor-alkali membrane electrolytic cells which are made by either flame spraying or plasma spraying a powder metal onto a cathode base surface. The cathode base surface is advantageously ferrous metal, such as steel, and the metal of the powder which is coated is one having a lower hydrogen overpotential than the ferrous metal of the base of the cathode. Coker et al specifically include nickel as one metal which can be used effectively in the Coker et al invention. Even more pertinent, Coker et al disclosed specific examples wherein two grades of METCO.TM. nickel powder are used as the powder which is plasma sprayed on a steel cathode. Nicolas et al describe cathodes for the electrolytic production of hydrogen which have an active surface consisting of oxide compounds of the spinel type. Applicant has now discovered that the useful results as disclosed by Coker et al can now be substantially improved while retaining the ease of manufacture of cathodes provided by the plasma or flame spraying processes.
In addition, applicant has discovered that oxidic surfaces comprising oxides other than oxides of the spinel type can be usefully employed as active hydrogen liberating cathodes. Applicant has also discovered that by modifying or otherwise altering the disclosed techniques of Hall et al and Brown et al, improved cathodes can be made or, in the case of the Brown et al cathode of the same character can be made more readily or more cheaply.